1. Field of the Invention
The invention relates generally to vacuum systems, and more particularly to mechanisms for automatically driving vacuum hoses.
2. Description of the Related Art
Central vacuum systems where a vacuum hose can be reeled between extended and retracted positions are known. An example of such a hose driving system in a wall mounted central vacuum system is found in U.S. Pat. No. 5,740,581 to Harrelson, II. A problem with a driven hose in a vacuum system is that normal movement of the hose between extended and retracted positions can occasionally be obstructed, where the hose gets jammed. Continued driving of the hose in such conditions risks damaging the hose. There is a need to detect when a jam condition occurs so that the driving mechanism can be terminated. It is known to measure the torque on an electric motor that drives a vacuum hose, and stop the motor when torque exceeds a predetermined value, assuming that increased torque means that a jam condition has occurred. See, for example, the Harrelson, II '581 patent.